Conventionally, for example, between a vacuum chamber as a vacuum container and a vacuum pump in a semiconductor manufacturing process, a pressure control valve with an isolation function may be provided. An isolation valve for vacuum is used to allow exhaust from the vacuum chamber or stop exhaust to make the inside of the vacuum chamber close to a predetermined vacuum pressure. When pressure is controlled by this isolation valve for vacuum, it is required that high sealability be ensured when the valve is closed, the flow rate be accurately controlled from a minute flow rate to a large flow rate at the time of flow rate adjustment and, even when the pressure is changed from atmospheric pressure to a low vacuum, the pressure be rapidly controlled with high accuracy as inhibiting an abrupt change of the degree of valve opening to prevent a turbulent flow and flying particles.
As an isolation valve for vacuum for use in a semiconductor manufacturing process, a butterfly pressure control valve is advantageously used in view of structural simplification, superiority in footprint ability, etc. As an isolation valve for vacuum of this type, for example, a butterfly pressure control valve of Patent Literature 1 has been suggested. This pressure control valve has a valve opening/closing mechanism including: a sheet ring which can move toward and away from a valve body by making reciprocating movements in a channel direction; an air channel for supplying air in a direction in which the sheet ring is moved away from the valve body; and a spring which presses the sheet ring in a direction of the valve body. In this valve, the sheet ring is moved toward and away from the valve body by air supply from the air channel and a pressing force of the spring to rotate the valve body, thereby allowing flow rate control with high accuracy.